EXC_BAD_ACCESS：核心數據，NSFetchedResultsController和numberOfRowsInSection

Question

在我的UITableViewController類，我有這樣的getter函數的NSFetchResultsController

-(NSFetchedResultsController*) fetchedResultsController { 

    if (_fetchedResultsController == nil) { 
     FlipPadAppDelegate* app = (FlipPadAppDelegate*) [[UIApplication sharedApplication] delegate]; 
     NSFetchRequest* fetchRequest = [[NSFetchRequest alloc] init]; 
     [fetchRequest setEntity: 
      [NSEntityDescription entityForName:@"FundClass" inManagedObjectContext:[app managedObjectContext]]]; 
     NSSortDescriptor* sortdesp = [[NSSortDescriptor alloc] initWithKey:@"name" ascending:YES]; 
     [fetchRequest setSortDescriptors:[NSArray arrayWithObject:sortdesp]]; 

     [fetchRequest setFetchBatchSize:20]; 

     _fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest 
                     managedObjectContext:[app managedObjectContext] 
                     sectionNameKeyPath:nil 
                        cacheName:@"_Stock"]; 


     _fetchedResultsController.delegate = self; 
     [fetchRequest release]; 
     [sortdesp release]; 

     NSError *error; 
     if (![[self fetchedResultsController] performFetch:&error]) { 
      // Handle error 
      NSLog(@"Unresolved error %@, %@", error, [error userInfo]); 

     } 
    } 

    return _fetchedResultsController; 

} 

不知何故，當應用程序運行到這一點，

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { 
    // Return the number of rows in the section. 
    id <NSFetchedResultsSectionInfo> sectionInfo = [[[self fetchedResultsController] sections] objectAtIndex:section]; 
    NSLog(@"numberOfRowsInSection %@", [sectionInfo numberOfObjects]); 
    return [sectionInfo numberOfObjects]; 

} 

它發生火災EXC_BAD_ACCESS

sqllite數據庫中有兩條記錄。

爲什麼這個例外？是否因爲我已將sectionNameKeyPath設置爲零？或者因爲我沒有將視圖的dataSource設置爲這個控制器？

Answer 1

因爲你正在登錄的對象@ 「numberOfRowsInSection％@」 和numberOfObjects是一個int：

@property (nonatomic, readonly) NSUInteger numberOfObjects 

使用@ 「numberOfRowsInSection％我」 代替。